Illuminated-display graduated scale device

ABSTRACT

A lightable indicator scale device is created, in particular, for a combination instrument in a motor vehicle, and has a dial which has a first lightable indicator scale in a first area, a second lightable indicator scale in a second area and a third lightable indicator scale in a third area; a first light source device for lighting the first lightable indicator scale and the third lightable indicator scale; a second light source device for lighting the second lightable indicator scale; and a light guide device arranged between the first and second light source devices, on the one hand, and the dial, on the other hand, designed such that it guides light beams of the first light source device to the first area and to the third area; it prevents light beams of the first light source device from reaching the second lightable indicator scale directly; it guides the light beams directed at the third area through the second area, without light scattering into the second lightable indicator scale; and it guide light beams of the second light source device to the second area without light scattering into the first and third lightable indicator scales.

FIELD OF THE INVENTION

The present invention relates to a lightable indicator scale device,and, in particular, a lightable indicator scale device for a combinationinstrument in a motor vehicle, having a dial which has a first lightableindicator scale in a first area, a second lightable indicator scale in asecond area and a third lightable indicator scale in a third area.

BACKGROUND INFORMATION

FIG. 2 shows a top view of a conventional lightable indicator scaledevice for a combination instrument in a motor vehicle, and FIG. 3 showsa cross-sectional view of the conventional lightable indicator scaledevice illustrated in FIG. 2.

FIGS. 2 and 3 show a first lightable indicator scale 1 in the form of akm/h scale, a second lightable indicator scale 2 in the form of a cruisecontrol scale, a third lightable indicator scale 3 in the form of an mphscale, beams of light L₁-L₃, a system carrier 4, a luminous disk ordiffusing panel 5, a liquid crystal display 6, a cold cathodefluorescent lamp 7, a dial 8 and a polarization filter 9.

With the lighting for the two concentrically arranged indicator scales 1and 3 in the combination instrument with cold cathode fluorescent lamp7, the cruise control segments between these two scales must beselectively switchable between lighted and unlighted.

Guarantee this, German Patent Application 195 47 375 A1 describes thatall three indicator scale 1, 2, 3 can be lighted with a single lightsource 7 as illustrated in FIG. 3. In system carrier 4, whichsimultaneously functions as a reflector, cold cathode fluorescent lamp 7is located beneath luminous disk 5 with liquid crystal display 6 aboveit, the latter being controllable locally in the area of the cruisecontrol scale. The cold cathode fluorescent lamp 7 lights up all threeindicator scales 1, 2 and 3, as illustrated by beams of light L₁, L₂ andL₃ passing through corresponding transparent or translucent passages indial 8 to the observer.

Two polarization filters 9 are arranged in the area of cruise controlscale 2. They are crossed so that no beam of light L₂ passes throughcruise control scale 2 to the observer when liquid crystal display 6 isnot activated, so that cruise control scale 2 appears dark in therespective indicator segment.

Selective activation of individual areas of liquid crystal display 6corresponding to the cruise control indicator segments makes it possiblefor incident beam of light L₂ to undergo a change in its polarization inthe area of liquid crystal display 6 and thus be able to pass throughcrossed polarization filters 9, so cruise control scale 2 appears brightin the respective indicator segment.

A disadvantage of the above described lightable indicator scale deviceis that the shape of liquid crystal display 6 must be adapted to that ofcruise control scale 2 (a horseshoe shape in the example illustratedhere) and therefore this display is complicated, sensitive and expensiveto manufacture, and both installation and removal are complicated.

SUMMARY OF THE INVENTION

A lightable indicator scale device according to the present inventionhas an advantage in that expensive liquid crystal displays which havecomplicated shapes, such as semicircles, can be eliminated for lightcontrol of the cruise control indicator segments and can be replaced bya simple independent second light source device which is expedientlyprovided only for the cruise control scale. For example, LEDs (lightemitting diodes) employing a simpler and less expensive control conceptin comparison with a liquid crystal display may be used for thispurpose.

The present invention contemplates that a light guide device is providedbetween the first and second light source devices, on the one hand, andthe dial, on the other hand, to split the light of the first lightsource device, i.e., the cold cathode fluorescent lamp, into the firstand third areas, which are separated by the dark second area which isfree of scattering. This second area corresponding to the secondindicator scale can be used for displaying information with the secondlight source device which is separated from the first light sourcedevice.

In one embodiment, the second lightable indicator scale is arrangedbetween the first lightable indicator scale and the third lightableindicator scale, and all three indicator scales are substantiallyconcentric.

In another embodiment, the first light source device is a cold cathodefluorescent lamp.

In another embodiment, the second light source device is an LEDarrangement, which can be controlled easily to selectively lightindicator segments of the second indicator scale.

In another embodiment, the first lightable indicator scale is arrangedsubstantially in front of the first light source device, and the thirdlightable indicator scale is offset to the side from the former.

In another embodiment, the first light source device is toroidal, theaxis of the cylinder arranged substantially normal to the viewingdirection, and the light guide device adjacent to the first light sourcedevice has a corresponding semicircular first cutout adjacent to thefirst light source device. This symmetry permits a relatively simpledesign of the light guide device.

In another embodiment, the light guide device has a triangular secondcutout adjacent to the dial. The light guide has an edge which preventsbeams of light from the first light source device from reaching thesecond indicator scale directly.

In another embodiment, the light guide device has substantiallyplane-parallel surfaces in the second area. This prevents input of lightfrom the first light source device into the second indicator scale, onthe one hand, while, on the other hand, preventing input of light fromthe second light source device into the first or third indicator scale.

In another embodiment, the light guide device has a chamfered area inthe third area for output of beams of light for lighting the thirdlightable indicator scale. This area, which is preferably stepped,ensures complete output of light at this point into the third indicatorscale.

In another embodiment, a system carrier is provided to hold the dial andthe light guide device.

In another embodiment, the system carrier functions as a reflector forthe first light source device in the first area.

In another embodiment, the system carrier has a lighting well for thesecond light source device in the second area. It is possible to obtainfrom the second light source device a directional or collimated lightbeam traversing the light guide device essentially in a straight line toreach the second indicator scale, i.e., the respective indicator segmentof the cruise control scale.

In another embodiment, the light guide device has a surface which isinclined so that incident beams are either allowed to pass through tothe first indicator scale or are deflected by total reflection such thatthey undergo total reflection again in the second area and thus do notlight the second indicator scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section of an embodiment of a lightable indicatorscale device according to the present invention.

FIG. 2 shows a top view of a conventional lightable indicator scaledevice for a combination instrument in a motor vehicle.

FIG. 3 shows a cross section of the conventional lightable indicatorscale device illustrated in FIG. 2.

DETAILED DESCRIPTION

Although it can be applied to any lightable indicator scale device, thepresent invention and an object of the present invention will beexplained with reference to a combination instrument on board a motorvehicle.

FIG. 1 shows a cross section of an embodiment of a lightable indicatorscale device according to the present invention.

In addition to the reference numbers already introduced, FIG. 1 shows amodified system carrier 4′, a light guide device 5′ instead of diffusingpanel 5, a first, second and third area 11, 12, 13 corresponding tofirst through third indicator scales 1 through 3, plane-parallelsurfaces 14, 15 of light guide device 5′ in second area 12, a chamferedarea 16 of light guide device 5′ in third area 13, a first semicircularcutout 17′ of light guide device 5′ in first area 11, a secondtriangular cutout 17″ of light guide device 5′ in first area 11, anedge-shaped cutout 17′″ of light guide device 5′ in first area 11, aninclined surface 17″″, an LED arrangement 18 and a lighting well 19. Thedesign and functioning of the lightable indicator scale device accordingto the embodiment shown here for a combination instrument in a motorvehicle are explained in greater detail below.

Dial 8 which has first lightable indicator scale 1 as a km/h scale infirst area 11, second lightable indicator scale 2 as a cruise controlscale in second area 12 and third lightable indicator scale 3 as an mphscale in third area 13 has substantially the same design as that of theconventional lightable indicator scale device illustrated in FIG. 3 asexplained above. Thus, second lightable indicator scale 2 is againarranged between first lightable indicator scale 1 and third lightableindicator scale 3, and all three indicator scales 1, 2, 3 aresubstantially concentric.

Modified system carrier 4′ functions in general to hold dial 8 and lightguide device 5′ and specifically as a reflector for first light sourcedevice 7 in first area 11.

By combining modified system carrier 4′, which functions as a reflectorin first area 11 at the same time, and the specially shaped luminousdisk, i.e., light guide device 5′, the beams of light of the first lightsource device in the form of cold cathode fluorescent lamp 7 are splitinto two areas 11, 13 having a high luminance, separated by area 12having a low luminance.

In this example, second light source device 18 is an LED arrangementwhich can selectively light only the cruise control indicator segments.

Light guide device 5′ arranged between first and second light sourcedevices 7, 18, on the one hand, and dial 8, on the other hand, isdesigned such that it guides light beams L₆ of first light source device7 to first area 11 and light beams L₅ of first light source device 7 tothird area 13 by using a specific design and arrangement as well as askillful utilization of the laws of refraction of light guide device 5′which is made of commercially available plexiglass, for example.

Light beams L₅ directed at third area 13 are guided through second area12 without resulting in light scattering into second lightable indicatorscale 2. Only light beams L₇ of second light source device 18 are guidedto second area 12 in second lightable indicator scale 2, andspecifically without light scattering into the first and third lightableindicator scales 1, 3.

The specific embodiment of light guide device 5′, its positioning onsystem carrier 4′ and the position of dial 8 on light guide device 5 andsystem carrier 4′ can be seen in FIG. 1.

First lightable indicator scale 1 is arranged substantially in front ofor above first light source device 7, i.e., in the extension of theviewing direction of an observer from above, and third lightableindicator scale 3 is offset to the side relative to first light sourcedevice 7.

The transparent cruise control indicator segments in the secondindicator scale on dial 8 are located exactly above lighting wells 19 insystem carrier 4′. To prevent the scattering of light from first lightsource device 7 into the cruise control indicator segments, the lightguide device has two plane-parallel surfaces 14, 15 in second area 12.The light is guided without scattering through the area of the cruisecontrol indicator segments in the parallel area of the luminous disk.

First light source device 7 is toroidal, the axis of the cylinderarranged substantially normal to the viewing direction, and light guidedevice 5′ adjacent to first light source device 7 has a correspondingfirst semiconductor cutout 17′ adjacent to first light source device 7.First semicircular cutout 17′ on the bottom of light guide device 5′weakens the luminance directly above the first light source device anddeflects the light into the side areas of light guide device 5′.

Light guide device 5′ is structured so that no beams of light of firstlight source device 7 can light the cruise control indicator segmentsdirectly. Light beam L₄ is a limiting case where incident light at thecritical angle of total reflection no longer reaches the cruise controlindicator segments directly.

Light guide device 5′ has a second, triangular cutout 17″ adjacent todial 8. All beams of light striking the upper interface of light guidedevice 5′ at a greater angle there undergo total reflection due to thechamfered shape, so that they can be output from the light guide deviceonly in the area of third indicator scale 3; this light guide device islocated above the stepped structure of chamfered area 16 which functionsto output beam of light L₅ into third indicator scale 3 at this point.

Beams of light L₆ striking the upper interface of the luminous disk at asmaller angle are output in the area of first indicator scale 1. Thelight guide has an edge 17′″ which prevents beams of light from thefirst light source device from reaching the second indicator scaledirectly.

Light guide device 5′ has surface 17″″ which is inclined so thatincident beams L₆ are either allowed to pass through to first indicatorscale 1 or are deflected by total reflection so that they undergo totalreflection L₅ again in second area 12 and thus do not light secondindicator scale 2.

The cruise control segments are lighted with the LEDs of LED arrangement18 which are placed beneath lighting wells 19. The plane-parallelstructure of light guide device 5′ in this area prevents the LED lightfrom being scattered next to the cruise control indicator segments, soit cannot contribute toward lighting of the same. In addition, thisgives a high contrast between lighted and unlighted indicator segments,because no light can be scattered into adjacent indicator segments.

The indicator segments of the cruise control can be lighted selectivelywith the LEDs, where first and third indicator scales 1, 3 can belighted at the same time over the entire area by cold cathodefluorescent lamp 7 without interferring reflections.

Although the present invention is described above on the basis of anexemplary embodiment, it is not limited to this embodiment but insteadcan be modified in a variety of ways.

In particular, the division of the dial and the shape of the scales arenot limited to the examples illustrated here and can be designed in manydifferent ways without departing from the scope of the presentinvention.

What is claimed is:
 1. A lightable indicator scale device, comprising: adial including a first lightable indicator scale in a firs area, asecond lightable indicator scale in a second area and a third lightableindicator scale in a third area; a first light source device lightingthe first lightable indicator scale and the third lightable indicatorscale; a second light source device lighting the second lightableindicator scale; and a light guide device arranged between the firstlight source device and the dial and between the second light sourcedevice and the dial, wherein the light guide device guides light beamsof the first light source device to the first area and to the thirdarea, wherein the light guide device prevents the light beams of thefirst light source device from reaching the second lightable indicatorscale directly, wherein the light guide device guides the light beams ofthe first light source device directed at the third area through thesecond area without light scattering into the second lightable indicatorscale, and wherein the light guide device guides light beams of thesecond light source device to the second area without light scatteringinto the first lightable indicator scale and the third lightableindicator scale.
 2. The lightable indicator scale device according toclaim 1, wherein the lightable indicator scale device is used for acombination instrument in a motor vehicle.
 3. The lightable indicatorscale device according to claim 1, wherein the second lightableindicator scale is arranged between the first lightable indicator scaleand the third lightable indicator scale, and wherein the first lightableindicator scale, the second lightable indicator scale and the thirdlightable indicator scale are substantially concentric.
 4. The lightableindicator scale device according to claim 1, wherein the first lightsource device includes a cold cathode fluorescent lamp.
 5. The lightableindicator scale device according to claim 1, wherein the second lightsource device includes a light-emitting-diode (LED) arrangement.
 6. Thelightable indicator scale device according to claim 1, wherein the firstlightable indicator scale is arranged substantially in front of thefirst light source device, and wherein the third lightable indicatorscale is offset from being arranged substantially in front of the firstlight source device.
 7. The lightable indicator scale device accordingto claim 6, wherein the first light source device is a toroid, alongitudinal axis of the toroid being arranged substantially normal to aviewing direction, and wherein the light guide device includes a convexcutout proximate to the first light source device.
 8. The lightableindicator scale device according to claim 7, wherein the light guidedevice prevents, via an edge, the light beams of the first light sourcedevice from reaching the second lightable indicator scale directly. 9.The lightable indicator scale device according to claim 1, wherein thelight guide device includes substantially parallel-plane surfaces in thesecond area.
 10. The lightable indicator scale device according to claim1, wherein the light guide device includes a chamfered area in the thirdarea, the chamfered area outputting the light beams of the first lightsource device, the outputted light beams lighting the third lightableindicator scale.
 11. The lightable indicator scale device according toclaim 1, further comprising: a system carrier holding the dial and thelight guide device.
 12. The lightable indicator scale device accordingto claim 11, wherein the system carrier reflects the light beams of thefirst light source device in the first area.
 13. The lightable indicatorscale device according to claim 11, wherein the system carrier includesa lighting well for the second light source device in the second area.14. The lightable indicator scale device according to claim 11, whereinthe light guide device includes a surface that is inclined so thatincident light beams are at least one of (1) allowed to pass through tothe first indicator scale and (2) deflected via total reflection suchthat the incident light beams undergo total reflection in the secondarea and do not light the second lightable indicator scale.